TRANSLOCATION OF 14C IN MACROCYSTIS INTEGRIFOLIA (PHAEOPHYCEAE)1,2

Translocation patterns in the giant kelp, Macrocystis integrifolia Bory, were investigated in situ using ¹⁴C tracer; sources and sinks were identified. Export was first detected after 4 h of labeling; experiments were routinely 24 h continuous ¹⁴C application. Mature blades exported ¹⁴C to young blades on the same frond and on younger fronds, as well as to sporophylls and frond initials at the bases of the fronds. Blades <0.3 m from the apex imported and did not export; this distance did not change seasonally. In spring export from blades 0.3–1.25 m from the apex was exclusively upwards; older blades also exported downwards. In fall downward export began 0.5 m from the apex, and blades >2 m from the apex exported exclusively downwards. Carbon imported by frond initials, young fronds, and sporophylls in fall may partly be stored for growth in early spring. No translocation was seen in very young plants until one blade (secondary frond initial) bad been freed from the apical blade; this blade exported to the apical blade for a time, but imported when it began to develop into a frond. The second and third formed blades on the primary fronds (sporophylls also exported when <0.3 m from the apex, and later stopped. Frond initials and sporophylls on later-formed fronds did not export at all. The translocation pattern in M. integrifolia differs from that previously reported in M. pyrifera in seasonal change and in distances from the apex at which the changes take place.     

HORMONAL CONTROL OF TRANSLOCATION OF PHOTOSYNTHETICALLY ASSIMILATED 14C IN YOUNG SOYBEAN PLANTS

The normal supply of growth substances to a young soybean plant was altered by removing the plant's apical meristem and replacing this meristem with an aqueous solution of either indole-3-acetic acid (IAA), gibberellic acid (GA), or water. The length of each experiment was 1 hr. In the middle of it, ¹⁴CO₂ was administered to one of the primary leaves of the plant, and at the end distribution of ¹⁴C in various parts of the plant was determined. It was found that an addition of growth substances stimulated translocation in three different ways. Both IAA and GA increased the total amounts of sucrose-¹⁴C translocated, increased the rate of its translocation, and affected the distribution pattern of translocated sucrose throughout the plant. Experiments using IAA-¹⁴C have shown that the action of IAA is on the longitudinal translocation in the stem and not on the transfer of photosynthate from the mesophyll to the conducting tissues of the leaf.     

CHANGES IN ORGAN FORMING CAPACITY OF CARROT ROOT CALLUSES DURING SUBCULTURES

1. The formation of buds and roots in seven strains of carrotrootcallus successively cultured for various periods on a mediumcontaining WHITE'S inorganic salts, sucrose, 2,4-D and yeastextract was investigated. 2,4-D completely suppressed organformation during stock subculturing. It was confirmed that theorgan forming capacity of the callus in a 2, 4-D-free test mediumdiminishes and finally completely disappears with prolongedperiods of previous subculturing of the callus.
2. IAA promotedthe root formation. Yeast extract, casein hydrolysateand aminoacids mixture promoted the bud formation of callusesat earlieststeps of subculturing (Phase I).
3. At next steps of subculturing(Phase II), IAA-dependent rootforming capacity of calluseswas lost although the bud formingcapacity induced by yeastextract, casein hydrolysate and aminoacids mixture was retained.
4. At further advanced steps of subculturing (Phase III), yeastextract induced only root formation, while casein hydrolysatestill could induce buds. IAA and amino acids mixture did notaffect the organ formation.
5. No organ formation was observedin calluses subcultured over38 months under any conditionsattempted (Phase IV).
6. Single cells or small cell clumps obtainedfrom the callus subculturedfor 2 months formed only roots onthe medium containing IAAand formed buds and roots on the mediumcontaining yeast extract.
7. These differences in organ formingcapacity and in responsestowards various factors are interpretedto reflect the changesin physiological states of the callusduring successive cultureson the stock culture medium.

(Received December 24, 1964; )     

RESPIRATORY METABOLISM IN THE PHLOEM, XYLEM AND CAMBIUM OF CARROT ROOT

Comparisons of respiratory metabolism among the phloem, cambiumand xylem of mature carrot root were carried out and the followingresults were obtained. 1) The activity of O₂ uptake on a dry weight basis in the cambiumwas higher than that in the xylem. The phloem showed the lowestactivity. 2) RQ was close to unity in all the three tissues.3) The inhibition rate of O₂ uptake by malonate was considerablyhigh in the three tissues. The highest inhibition was observedin the cambium. 4) In the phloem and xylem the malonic inhibitionrate of ¹⁴CO₂ release from G-U-¹⁴C was not so high as comparedwith that of O₂ uptake. In the cambium, however, those of O₂uptake and ¹⁴CO₂ output were comparable. 5) Malonate treatmentdid not cause any significant change in RQ. 6) The C₆/C₁ ratiowas highest in the cambium and lowest in the phloem. From these it is concluded that the participation of the TCAcycle in respiration is great in all the three tissues of carrotroot, and among the three the cambium has the highest activityof the cycle. As for the PP pathway, the xylem and phloem havea higher activity than the cambium. (Received April 11, 1967; )     

TRANSLOCATION OF C14-LABELED PHOTOSYNTHATE IN NODULATED LEGUMES AS INFLUENCED BY NITRATE NITROGEN

Translocation of C¹⁴-labeled photosynthate was studied in nodulated pea and subterranean-clover plants which were grown either continuously without combined nitrogen or exposed to NaNO₃ in the nutrient solution for five days prior to C¹⁴O₂ assimilation. Supplying combined nitrogen decreased the proportion of photosynthate translocated to nodules with a corresponding increase in the proportion going to roots. Nodules on plants grown without combined nitrogen had a higher radioactivity than nodules on plants treated with sodium nitrate.     

CHANGES IN THE RESPONSE OF CARROT ROOT CALLUSES TO THE ROOT EXTRACT OCCURRING DURING THEIR SUCCESSIVE CULTURES

1. Alcohol extract of carrot root promoted the growth of the carrotroot callus which had been succesively cultured for more than18 months (CCL) on the medium containing WHITE'S inorganic salts,sucrose, yeast extract and 2, 4-D, but only a weak promotionwas observed for the growth of the carrot root callus whichhad been cultured for less than 14 months (CCS).
2. The activesubstances were fractionated by Amberlite IR-120and AmberliteIRA-400 into four fractions; C, D, E, and F. Eachfraction seemedto act synergistically to produce the effectof the whole carrotroot extract on the growth of CCL.
3. Fraction F of the carrotroot extract, which was adsorbed byAmberlite IRA-400 but notby Amberlite IR-120, promoted thegrowth of CCL in the presenceof other fractions, but had noeffect on the growth of CCS.So the different responses to thealcohol extract of the carrotroot calluses having differentlengths of successive cultureperiod seemed to depend mainlyon the ability of respondingto fraction F.
4. Using four strains of carrot root callusesof different origin,it was ascertained that different responsesof carrot root callusesto fraction F depended on the lengthof their culture and noton their strain-specific characters.
5. The substances active for the growth of CCL in the carrotrootextract passed through a dialysis membrane. These substanceswere little affected by autoclaving and remained in the aqueouslayer when shaken with several organic solvents: n-butanol,ethyl acetate, chloroform, benzene, ethyl ether and carbon tetrachloride.
6. Alcohol extract of carrot root also promoted the growth ofcarrotroot explant, tobacco stem callus and sunflower crowngall tissue.

(Received December 24, 1964; )     

CHANGES IN RESPONSE TO PURINE AND PYRIMIDINE DERIVATIVES OF CARROT ROOT CALLUS DURING SUCCESSIVE CULTURING

1. The growth of the carrot root callus which had been subculturedfor a long period (CCL) was promoted by the addition of 5l0^–8and 5l0^–7 M kinetin, whereas in the callus subculturedfor a short period (CCS) no growth promotion was observed atany concentrations of kinetin tested.
2. CCL showed an increasedgrowth in response to the applicationof kinetin, guanine, adenine,hypoxanthine, uracil, thymine,and cytosine in the presenceof fractions A and C of carrotroot extract, whereas no suchresponse was observed in CCS.CCL required fraction C to respondto uracil and probably purineand pyrimidine derivatives ingeneral.
3. The growth of CCL was promoted by kinetin, guanine,adenine,or hypoxanthine in the medium containing inositol andaminoacids mixture. In this case the growth-promoting actionof guanine,adenine, or hypoxanthine was nullified by kinetin.

(Received December 24, 1964; )     

PHYSIOLOGICAL AND BIOCHEMICAL CHANGES OF CARROT ROOT CALLUS DURING SUCCESSIVE CULTURES

1. The longer the period of stock culture, the more remarkableis the growth inhibition by 8-azaguanine in callus.
2. Chloramphenicol,5-methyltryptophane and mitomycin C exert greaterinhibitionon growth in CCL than in CCS.
3. Bud formation is inhibited bysome concentrations of chloramphenicolwithout accompanyinginhibition of the growth.
4. Cell size and the contents of RNA,DNA, protein and lipid percell of CCL are greater than thoseof CCS, respectively. Thecontents per cell of RNA and lipidin "mitochondrial fraction"are higher in CCL than in CCS.
5. Incorporationof guanine-8-¹⁴C into RNA of CCS occurs rapidlyin the first12 hr and slows down thereafter, but that in CCL-RNAincreasessteadily for 16 hr. This difference in rate of theincorporationafter 12 hr between CCS and CCL is principallydue to the differencein rate of the incorporation into RNAof nuclear, mitochondrialand soluble fractions.

1. The rate of RNA breakdown in CCL wasnot so great as the rateof synthesis.
2. 8-azaguanine (10^–3and 10^–4M) inhibits incorporationof guanine-8.¹⁴C intoRNA of both CCS and CCL during 14 hr,but thereafter (up to25 hr) it inhibits the incorporation intoCCL-RNA alone leavingthat into CCS-RNA unaffected.

1. In CCL 510^–5M 8.azaguaninedoes not affect total radioactivityincorporated into bulk RNA,but inhibits incorporation intoRNA of "mitochondrial fraction".

(Received December 23, 1964; )     

TRANSLOCATION IN MACROCYSTIS. III. COMPOSITION OF SIEVE TUBE EXUDATE AND IDENTIFICATION OF THE MAJOR C14-LABELED PRODUCTS1

The major C¹⁴-labeled substance in sieve tube exudate of M. pyrifera is D-mannitol, comprising 3.6% (w/v). No sugars are detectable. Certain amino acids also possess some CWabeling and occur in significantly high concentrations in exudate. The exudate contains negligible ether-soluble lipid, but has a large amount of protein and a high concentration of K⁺. Neither protein nor lipid become labeled significantly in sieve tubes during short-term translocation experiments with C¹⁴. In general the chemical composition of the assimilate stream is comparable to that of vascular plants and does not, consequently, necessitate a different mechanism for translocation.     

细胞分裂素在离体蒜苔内的运转

离体蒜苔饲喂带~3H 标记的6-苄基腺嘌呤(BA)后在暗中25℃下放置,分别在第3、5、10、15、20天取样,进行放射性物质的分布分析。结果表明:(1)BA 能沿着苔茎大量、长距离地上运,并在顶端的珠蒜中积累;(2)BA 的这种运转具有很强的向顶极性;(3)这种运转是一个平缓而稳定的过程,珠蒜中 BA 的积累与时间成较好的线性关系;(4)顶端的珠蒜对 BA 的上运是必不可少的。根据以上结果,本文对蒜苔内 BA 的运转机理及意义进行了讨论。     

THE BIOLOGY OF HARVEYELLA MIRABILIS (CRYPTONEMIALES,RHODOPHYCEAE). VI. TRANSLOCATION OF PHOTOASSIMILATED 14C122

Pulse-chase labelling experiments demonstrate that photoassimilated ¹⁴C-bicarbonate is translocated from the host red alga Odonthalia floccosa (Esper) Falkenberg to the parasite Harveyella mirabilis (Reinsch) Schmitz & Reinke. The primary path of translocation is from host cortical cells (the site of photoassimilation) to the erumpent parasite pustule via the zone of interdigitation. The latter is a tissue region in which rhizoidal cells of Harveyella grow between, and establish secondary pit plugs with medullary cells of Odonthalia. A secondary translocation pathway occurs from isolated host cells dispersed in the pustule of Harveyella to adjacent parasite cells.     

TRANSLOCATION OF APPLIED GIBBERELLIN IN BEAN SEEDLINGS

The direction and extent of GA transport in Pinto beans has been studied. The increase in growth rate was used as a measure of the amount of GA which reached the stem apex. The evidence showed that a similar increase in stem growth occurred whether GA was applied to the first trifoliolate leaf or to the apex of the shoot, but considerably less elongation resulted when GA was applied to primary leaves. When leaves were treated with GA after remaining in darkness for extended times, no increase in stem elongation was observed; however, growth was promoted when the plants were returned to light. The time required for a sufficient amount of GA to be translocated from the leaf to increase stem growth is less than 1 hour. The maximum growth response was found when the treated leaf was left on the plant for 3 or more hours. A study of GA movement in two-branched plants was made. The untreated branch showed no growth response when GA was applied to the apex of the other branch, even if the dose of GA was 20 × greater than a saturating dose. Similar results were observed when GA was applied to the first trifoliolate leaf. Considerable GA moved from a mature leaf to the opposite shoot if this untreated branch had been defoliated. The pattern of GA movement to the opposite shoot was dependent on the position of the treated leaf on the shoot. It is concluded that the movement of applied GA is related to carbohydrate transport within the plant.     

RADIOAUTOGRAPHIC STUDY OF TRANSLOCATION IN BEAN LEAVES

The movement of the radioactivity from sucrose, indole-3-acetic acid (IAA) and phosphate has been examined in excised bean leaves. Preferential translocation of the labelled materials toward the base of leaf and petiole was demonstrated, suggesting a natural mobilization gradient down the leaf and petiole. Establishment of other mobilization centers in the leaf by local application of N⁶-benzyladenine diverted the movement of the sucrose label and, to a lesser extent, the phosphate label. There was no apparent mobilization of IAA by benzyladenine. Evidence is provided that there is a continuity of label from the source to the sink regions, and it is suggested that reported instances of noncontinuity of label may be attributable to the refixation of respired C¹⁴O₂ by tissue treated with benzyladenine. The observations appear to substantiate the concept that the unloading of solutes from the phloem can regulate the direction and intensity of translocation.